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Chemistry LibreTexts

1. Assembly of Plexiglas Interlock Box

The Plexiglas Interlock Box serves as a guard against electric shock. The box is made using Plexiglas bonded with acetone and incorporates a Single Pole Double Throw (SPDT) switch which prevents current flow from the high voltage supply when the box lid is open (like when changing vials). If the box lid is open, current will not flow even if the power supply is turned on and at its maximum setting.

  1. The Interlock box is a 21 cm cube made of Plexiglas with a thickness of approximately ¾ mm. The sides are bonded with acetone.
  2. A hinge should be on the top of the box so that it can be opened to access the sample holder. See Figure 1.
  3. There should be 2 or 3 holes in each side of the Plexiglas box to accommodate the pressure tubing, electrodes, and capillary.

    Plexiglass Interlock Box

  4. A SPDT switch (Radioshack, #275-016 or #275-017) is attached to the upper front corner of the interlock box using hot glue. The switch should be mounted such that it is closed when the interlock box is closed and open when the interlock box is open.

    Single Pole-Double Throw (SPDT) Switch

  5. The switch is connected to the HV Power Supply using 2 lengths of 24-gauge wire. One length connects the switch to post 9 of the pin rack on the back of the power supply. The second length connects the switch to post 10 of the pin rack on the back of the power supply. Once connected, current can only follow from the HV Power Supply when the SPDT switch is closed.

    Power Supply (Rear View)

    Picture 3, the pin rack on the back of the Spellman HV Power Supply (#CZE1000R). The green and black posts are connected to the SPTD switch on the interlock box. Posts 2-3, 4-5, and 11-12 (marked red) must be connected to each other for the power supply to function properly.

  6. The interlock box should be positioned between the power supply and the UV-vis absorbance detector.

Home-built CE System